Modular front drivetrain assembly

ABSTRACT

An apparatus and methods are provided for a modular front drivetrain comprising a single assembly that may be installed onto and removed from a vehicle. The modular front drivetrain comprises a modular chassis supporting a transaxle, a front differential, and a steering gear for operating front wheels of the vehicle. The transaxle, the front differential and drive axles convey torque from an engine onboard the vehicle to the front wheels. A spindle assembly is coupled with each front wheel of the vehicle and pivotally joined with the modular chassis by way of a front suspension system. Steering rods coupled with the spindle assemblies horizontally rotate the front wheels according to operation of a steering wheel onboard the vehicle. The modular front drivetrain advantageously facilitates replacing an entire drivetrain and suspension assembly quickly and easily in the event of a part failure during racing applications.

PRIORITY

This application claims the benefit of and priority to U.S. ProvisionalApplication, entitled “Modular Front Drivetrain Assembly,” filed on Sep.14, 2019 and having application Ser. No. 62/900,481, the entirety ofsaid application being incorporated herein by reference.

FIELD

Embodiments of the present disclosure generally relate to the field ofvehicle drivetrains. More specifically, embodiments of the disclosurerelate to an apparatus and methods for a modular front drivetraincomprising a single assembly that may be installed onto and removed froma vehicle.

BACKGROUND

A double wishbone suspension is a well-known independent suspensiondesign using upper and lower wishbone-shaped arms to operably couple afront wheel of a vehicle. Typically, the upper and lower wishbones orsuspension arms each has two mounting points to a chassis of the vehicleand one mounting joint at a spindle assembly or knuckle. A shockabsorber and a coil spring may be mounted onto the wishbone to controlvertical movement of the front wheel. The double wishbone suspensionfacilitates control of wheel motion throughout suspension travel,including controlling such parameters as camber angle, caster angle, toepattern, roll center height, scrub radius, scuff, and the like.

Double wishbone suspensions may be used in a wide variety of vehicles,including heavy-duty vehicles, as well as many off-road vehicles, asshown in FIG. 1. FIG. 1 shows an off-road vehicle 100 that is of a Sideby Side variety. The Side by Side is a four-wheel drive off-road vehiclethat typically seats between two and six occupants and is sometimesreferred to as a Utility Task Vehicle (UTV), a Recreational Off-HighwayVehicle (ROV), or a Multipurpose Off-Highway Utility Vehicle (MOHUV). Inaddition to the side-by-side seating arrangement, many UTVs have seatbelts and roll-over protection, and some may have a cargo box at therear of the vehicle. A majority of UTVs come factory equipped with hardtops, windshields, and cab enclosures.

The double-wishbone suspension often is referred to as “double A-arms,”although the arms may be A-shaped, L-shaped, J-shaped, or even a singlebar linkage. In some embodiments, the upper arm may be shorter than thelower arm so as to induce negative camber as the suspension jounces(rises). Preferably, during turning of the vehicle, body roll impartspositive camber gain to the lightly loaded inside wheel, while theheavily loaded outer wheel gains negative camber.

The spindle assembly, or knuckle, is coupled between the outboard endsof the upper and lower suspension arms. In some designs, the knucklecontains a kingpin that facilitates horizontal radial movement of thewheel, and rubber or trunnion bushings for vertical hinged movement ofthe wheel. In some relatively newer designs, a ball joint may bedisposed at each outboard end to allow for vertical and radial movementof the wheel. A bearing hub, or a spindle to which wheel bearings may bemounted, may be coupled with the center of the knuckle.

Constant velocity (CV) joints allow pivoting of the suspension arms andthe spindle assembly, while a drive shaft coupled to the CV jointdelivers power from a transaxle to the wheels. Although CV joints aretypically used in front wheel drive vehicles, off-road vehicles such asfour-wheeled buggies comprise CV joints at all wheels. Constant velocityjoints typically are protected by a rubber boot and filled withmolybdenum disulfide grease.

Given that off-road vehicles routinely travel over very rough terrain,such as mountainous regions, there is a desire to improve the mechanicalstrength and performance of off-road drivetrain and suspension systems,while at the same reducing the mechanical complexity of such systems.

SUMMARY

An apparatus and methods are provided for a modular front drivetraincomprising a single assembly that may be installed onto and removed froma vehicle. The modular front drivetrain comprises a modular chassissupporting a transaxle, a front differential, and a steering gear foroperating front wheels of the vehicle. The transaxle and frontdifferential are configured to convey torque from an engine onboard thevehicle to the front wheels. A spindle assembly is coupled with eachfront wheel of the vehicle and pivotally joined with the modular chassisby way of a front suspension system. A drive axle is engaged with thefront differential and each spindle assembly for conveying torque to thefront wheels. Steering rods coupled with the spindle assemblies areconfigured for horizontally rotating the front wheels according tooperation of a steering wheel onboard the vehicle. The modular frontdrivetrain is configured to facilitate a practitioner replacing anentire drivetrain and suspension quickly and easily in the event of apart failure.

In an exemplary embodiment, a modular front drivetrain for operatingfront wheels of a vehicle comprises: a modular chassis supporting adrivetrain and a steering system operatively coupled with the frontwheels; a spindle assembly coupled with each front wheel; and a frontsuspension system coupling each spindle assembly to the modular chassis.

In another exemplary embodiment, the modular front drivetrain comprisesa single drivetrain and suspension assembly that is configured to beinstalled onto and removed from the vehicle. In another exemplaryembodiment, the modular front drivetrain is configured to facilitate apractitioner replacing an entire drivetrain and suspension quickly andeasily in the event of a part failure.

In another exemplary embodiment, the front suspension system includes anupper control arm and a lower control arm that are configured to couplethe front wheel with the modular chassis. In another exemplaryembodiment, the upper control arm comprises two inboard upper controlarm joints that couple the upper control arm to the modular chassis andan outboard upper control arm joint that couples the upper control armto the spindle assembly. In another exemplary embodiment, the lowercontrol arm includes two inboard lower control arm joints that couplethe lower control arm to the modular chassis and an outboard lowercontrol arm joint that couples the lower control arm to the spindleassembly. In another exemplary embodiment, the upper control arm and thelower control arm are configured to facilitate vertical motion of thefront wheel during travel over terrain and accommodate horizontal motionof the front wheel during steering of the front wheel by way of thesteering gear. In another exemplary embodiment, a strut that iscomprised of a shock absorber and a coil spring is mounted to the lowercontrol arm by way of a lower pivot; and wherein a top of the strut iscoupled to an upper pivot disposed on a chassis of the vehicle.

In another exemplary embodiment, the drivetrain includes a transaxle, afront differential and a drive axle coupled between each front wheel andthe front differential. In another exemplary embodiment, the drive axleis configured to conduct torque from the transaxle to the front wheeland accommodate vertical pivoting motion of the front suspension systemin response to road conditions. In another exemplary embodiment, thedrive axle includes a constant velocity joint that is coupled with thespindle assembly and configured to allow uninterrupted torquetransmission from the transaxle to the front wheel during verticalpivoting of the front suspension assembly due to road conditions.

In another exemplary embodiment, the steering system includes a steeringrod coupled between each spindle assembly and a steering gear disposedon the modular chassis. In another exemplary embodiment, the steeringgear is configured to cause the front wheels to articulate horizontallywith respect to the modular chassis upon the steering gear being turnedby way of a steering wheel of the vehicle. In another exemplaryembodiment, the steering rod is coupled with each spindle assembly byway of a steering rod-end joint configured to allow vertical andhorizontal rotational motion of the spindle assembly during operation ofthe vehicle. In another exemplary embodiment, the steering rod-end jointis coupled with each spindle assembly forward of a drive axle so as toprovide a leading-edge steering system to the vehicle.

In an exemplary embodiment, a method for a modular front drivetrain foroperating front wheels of a vehicle comprises: configuring a modularchassis for supporting a drivetrain to convey torque from an engineonboard the vehicle to the front wheels; coupling each front wheel tothe modular chassis by way of a spindle assembly and a front suspensionsystem; communicating torque from the drivetrain to the front wheel byway of a front differential and drive axles; coupling a braking systemwith the drive axles for slowing rotation of the front wheels; disposinga steering system on the modular chassis for directing horizontal motionof the front wheels; and installing the modular front drivetrain ontothe vehicle.

In another exemplary embodiment, the method further comprisesconfiguring the modular front drivetrain as a single drivetrain andsuspension assembly to be installed onto and removed from the vehicle.In another exemplary embodiment, coupling includes configuring the frontsuspension system to allow vertical motion of the front wheels due toroad conditions. In another exemplary embodiment, disposing includescoupling a steering rod between each spindle assembly and a steeringgear disposed on the modular chassis. In another exemplary embodiment,coupling the steering rod includes coupling a steering rod-end jointwith each spindle assembly forward of the drive axles to provide aleading-edge steering system to the vehicle. In another exemplaryembodiment, communicating torque includes coupling each drive axle withthe spindle assembly by way of a constant velocity joint configured toallow uninterrupted torque transmission from the transaxle to the frontwheel during vertical pivoting of the front suspension assembly due toroad conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings refer to embodiments of the present disclosure in which:

FIG. 1 illustrates an exemplary embodiment of an off-road vehicle thatis particularly suitable for implementation of a modular frontdrivetrain in accordance with the present disclosure;

FIG. 2 illustrates an upper perspective view of a driver-side portion ofan exemplary embodiment of a modular front drivetrain;

FIG. 3 illustrates a front view of the modular front drivetrain of FIG.2; and

FIG. 4 illustrates an upper perspective view of a driver-side portion ofan exemplary embodiment of a modular front drivetrain.

While the present disclosure is subject to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Theinvention should be understood to not be limited to the particular formsdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the present disclosure.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present disclosure. Itwill be apparent, however, to one of ordinary skill in the art that theinvention disclosed herein may be practiced without these specificdetails. In other instances, specific numeric references such as “firstjoint,” may be made. However, the specific numeric reference should notbe interpreted as a literal sequential order but rather interpreted thatthe “first joint” is different than a “second joint.” Thus, the specificdetails set forth are merely exemplary. The specific details may bevaried from and still be contemplated to be within the spirit and scopeof the present disclosure. The term “coupled” is defined as meaningconnected either directly to the component or indirectly to thecomponent through another component. Further, as used herein, the terms“about,” “approximately,” or “substantially” for any numerical values orranges indicate a suitable dimensional tolerance that allows the part orcollection of components to function for its intended purpose asdescribed herein.

A double wishbone suspension generally comprises upper and lowersuspension arms that operably couple a front wheel of a vehicle. Theupper and lower suspension arms each typically include two mountingpoints to a chassis of the vehicle and one mounting joint at a spindleassembly. The spindle assembly is coupled between the outboard ends ofthe upper and lower suspension arms and is configured to allow verticaland horizontal radial movement of a wheel coupled with the spindleassembly. Constant velocity (CV) joints allow pivoting of the suspensionarms and the spindle assembly, while a drive shaft coupled to the CVjoint conveys power from a transaxle to the wheel. Given that off-roadvehicles routinely travel over very rough terrain, such as mountainousregions, there is a desire to improve the mechanical strength andperformance of off-road drivetrain and suspension systems, while at thesame reducing the mechanical complexity of such systems. Embodiments ofthe disclosure provide to a modular front drivetrain comprising a singleassembly that may be installed onto and removed from a vehicle.

FIG. 1 shows an off-road vehicle 100 that is particularly suitable forimplementation of a modular front drivetrain in accordance with thepresent disclosure. As disclosed hereinabove, the off-road vehicle 100generally is of a Utility Task Vehicle (UTV) variety that seats twooccupants, includes a roll-over protection system 104, and may have acab enclosure 108. Rear wheels 112 of the off-road vehicle 100 may beoperably coupled with a chassis 116 by way of a trailing arm suspensionsystem. Front wheels 120 may be operably coupled with the chassis 116 byway of a front suspension system and a spindle assembly. It should beunderstood, however, that the modular front drivetrain disclosed hereinis not to be limited to the off-road vehicle 100, but rather the modularfront drivetrain may be incorporated into a wide variety of vehicles,other than UTVs, without limitation.

FIG. 2 illustrates an upper perspective view of a driver-side portion ofan exemplary embodiment of a modular front drivetrain 124 that may beimplemented in the off-road vehicle 100. The modular front drivetrain124 includes a modular chassis 128 that supports a transaxle 132, afront differential 136, and a steering gear 140 that are operablycoupled with a spindle assembly 144 and the front wheel 120 by way of afront suspension system 148. Further, the modular chassis 128 providesmounting points for the front suspension 148, in lieu of conventionalmounting points that comprise portions of the chassis 116 of thevehicle. It is to be understood, therefore, that the modular frontdrivetrain 124 comprises a single drivetrain/suspension assembly thatmay be installed onto and removed from the vehicle 100, unlike aconventional drivetrain and suspension that comprise multiple componentsthat must be individually assembled onto the chassis 116 of the vehicle.

The front suspension system 148 includes an upper control arm (UCA) 152and a lower control arm (LCA) 156 that couple the front wheel 120 withthe modular chassis 128. The UCA 152 comprises two inboard UCA joints160 that couple the UCA 152 to the modular chassis 128 and an outboardUCA joint 164 that couples the UCA 152 to the spindle assembly 144. Asbest shown in FIG. 3, the LCA 156 includes two inboard LCA joints 168that couple the LCA 156 to the modular chassis 128 and an outboard LCAjoint 172 that couples the LCA 156 to the spindle assembly 144. As willbe recognized, the UCA and LCA 152, 156 generally are of a doublewishbone variety of suspension that facilitates vertical motion of thefront wheel 120 during travel over terrain, as well as facilitatinghorizontal motion of the front wheel 120 during steering of the vehicle100 by way of the steering gear 140. The UCA and LCA 152, 156 furtherfacilitate controlling various parameters affecting the orientation ofthe front wheel 120 with respect to the off-road vehicle 100, such as,by way of non-limiting example, camber angle, caster angle, toe pattern,roll center height, scrub radius, and scrub.

It should be understood that although the front suspension system 148 isdisclosed specifically in connection with the driver-side of theoff-road vehicle 100, a passenger-side front suspension system is to becoupled with a passenger side of the modular chassis 128. It should befurther understood that the passenger-side front suspension system issubstantially identical to the driver-side front suspension system 148,with the exception that the passenger-side front suspension system isconfigured specifically to operate with the passenger-side of themodular chassis 128. As will be appreciated, therefore, thepassenger-side front suspension system and the driver-side frontsuspension system 148 may be configured as reflections of one anotheracross a longitudinal midline of the off-road vehicle 100.

As shown in FIGS. 2-3, a strut 176 that is comprised of a shock absorberand a coil spring is mounted to the LCA 156 by way of a lower pivot (notshown). A top of the strut 176 is coupled to an upper pivot (not shown)that may be disposed on the chassis 116 of the vehicle 100. The strut176 is configured to dampen vertical motion of the front suspensionsystem 148 due to movement of the front wheel 120 as the vehicle 100travels over terrain. The UCA 152 may be suitably configured, such as inthe form of a J-arm, so as to facilitate coupling the strut 176 betweenthe LCA 156 and the chassis 116 (see FIG. 1) of the vehicle 100 in lieuof being coupled between the UCA 152 and the chassis 116. Moreover, itis contemplated that in some embodiments, the strut 176 may be coupledbetween the LCA 156 and the modular chassis 128, without limitation, andwithout deviating beyond the scope of the present disclosure.

As best shown in FIG. 2, a drive axle 180 is coupled between the frontwheel 120 and the front differential and transaxle 136, 132. The driveaxle 180 is configured to conduct torque from the transaxle 132 to thefront wheel 120 and accommodate vertical pivoting motion of the frontsuspension system 148 in response to road conditions, as isstraightforward to see upon comparing FIG. 3 and FIG. 4. As best shownin FIG. 3, the drive axle 180 includes a constant velocity (CV) joint184 that is coupled with the spindle assembly 144. The CV joint 184enables uninterrupted torque transmission from the transaxle 132 to thefront wheel 120 during vertical pivoting of the front suspensionassembly 148 due to road conditions.

In the embodiment illustrated in FIGS. 2-3, a steering rod 188 couplesthe spindle assembly 144 with the steering gear 140 disposed on themodular chassis 128. The steering rod 188 may be coupled with thespindle assembly 144 by way of a steering rod-end joint 192 that issimilar to the inboard UCA joints 160. It is contemplated, therefore,that the steering rod-end joint 192 may be of a Heim-joint variety ormay be of a bushing variety, as desired. As will be appreciated, thesteering rod-end joint 192 allows vertical and horizontal rotationalmotion of the spindle assembly 144 during operation of the vehicle 100.

Moreover, the steering rod-end joint 192 is coupled with the spindleassembly 144 forward of the drive axle 180, thereby providing aleading-edge steering system to the vehicle 100. Experimentation hasdemonstrated that the leading-edge steering system shown in FIGS. 2-3advantageously decreases leverage of the front wheel 120 on the steeringrod-end joint 192 and the steering rod 188, thereby substantiallyeliminating bump steer that may occur due to forces exerted on the frontwheel 120 by rough terrain. Details pertaining to rod-end joints aredisclosed in above-mentioned U.S. patent application Ser. No.15/625,692, which is entitled “Rod-End Front Suspension.” Further,details pertaining to leading-edge steering systems are disclosed inU.S. patent application Ser. No. 15/625,813, entitled “Leading-EdgeSteering Assembly,” filed on Jun. 16, 2017, the entirety of which isincorporated herein by reference.

Turning again to FIG. 2, the modular front drivetrain 124 may furtherinclude a braking system configured to enable a practitioner to slow therotation rate of the front wheel 120 during operation of the vehicle100. In the illustrated embodiment of FIGS. 2-3, the brake systemcomprises a brake caliper 196 that is fastened onto the modular chassis128. A brake disc 200 is coupled to the drive axle 180 such that aperiphery of the brake disc 200 passes within the brake caliper 196. Aswill be recognized, when the practitioner depresses a brake pedal of thevehicle 100 the brake caliper 196 applies pressure to the brake disc200, thus slowing the rotation rate of the front wheel 120. The brakecaliper 196 may be cable operated or may be operated by way hydrauliclines. Although not shown in FIGS. 2-3, the brake disc 200 may becoupled with a hub comprising the front differential 136. In someembodiments, however, the brake disc 200 may be coupled with a constantvelocity joint that is coupled with the hub of the front differential136. It is contemplated that the brake caliper 196 and the brake disc200 may be incorporated into the modular front drivetrain 124 in a widevariety of configurations, without limitation, and without deviatingbeyond the scope of the present disclosure.

As disclosed hereinabove, the modular front drivetrain 124 comprises amodular chassis 128 that supports the transaxle 132, the frontdifferential 136, the drive axle 180 and the front suspension system148, such that engine torque applied to the transaxle 132 is conveyed tothe front wheel 120. The modular chassis 128 also supports the steeringgear 140 and the steering rod 188, such that turning the steering gear140, by way of a steering wheel of the vehicle 100, causes the frontwheel 120 to articulate horizontally with respect to the modular chassis128. Further, the modular chassis 128 provides mounting points for thefront suspension 148 that allow the front wheel 120 to move verticallyfrom a low position (e.g., due to “maximal bounce”), shown in FIG. 3, toa high position (e.g., due to “maximal bump”), shown in FIG. 4. As such,the modular front drivetrain 124 is not limited to the specificconfiguration shown in FIGS. 2-3, but rather the configuration of themodular front drivetrain 124 may be varied in accordance with theconfiguration of each of the components comprising the modular frontdrivetrain 124, without limitation.

Moreover, the modular front drivetrain 124 generally may be varied inaccordance with the specific type of vehicle 100 into which the modularfront drivetrain 124 is to be implemented. It is contemplated that themodular front drivetrain 124 may be implemented in any of variousoff-road vehicles 100, such as, by way of non-limiting example, UtilityTask Vehicles (UTVs), Recreational Off-Highway Vehicles (ROVs), orMultipurpose Off-Highway Utility Vehicles (MOHUVs), without limitation.As such, the modular front drivetrain 124 is particularly well-suitedfor off-road racing applications, such as desert racing, short courseracing, hill climbing, rallying, and the like.

In addition to the off-road applications discussed above, it iscontemplated that, in some embodiments, the modular front drivetrain 124may be incorporated into racing vehicles that are not necessarilyintended for off-road racing. For example, the modular front drivetrain124 may be incorporated into racing vehicles that may be used for any offormula racing, sports car racing, stock car racing, drag racing,touring car racing, production car racing, as well as amateur open-wheelracing applications, such as karting, and the like. In suchapplications, the modular front drivetrain 124 advantageously enables anentire drivetrain and suspension assembly to be quickly and easilyreplaced in the event of a part failure, unlike in the case ofconventional racing vehicles that may be sidelined during a race due tothe failure of an individual part comprising the drivetrain or thesuspension.

While the invention has been described in terms of particular variationsand illustrative figures, those of ordinary skill in the art willrecognize that the invention is not limited to the variations or figuresdescribed. In addition, where methods and steps described above indicatecertain events occurring in certain order, those of ordinary skill inthe art will recognize that the ordering of certain steps may bemodified and that such modifications are in accordance with thevariations of the invention. Additionally, certain of the steps may beperformed concurrently in a parallel process when possible, as well asperformed sequentially as described above. To the extent there arevariations of the invention, which are within the spirit of thedisclosure or equivalent to the inventions found in the claims, it isthe intent that this patent will cover those variations as well.Therefore, the present disclosure is to be understood as not limited bythe specific embodiments described herein, but only by scope of theappended claims.

What is claimed is:
 1. A modular front drivetrain for operating frontwheels of a vehicle, the modular front drivetrain comprising: a modularchassis supporting a drivetrain and a steering system operativelycoupled with the front wheels; a spindle assembly coupled with eachfront wheel; and a front suspension system coupling each spindleassembly to the modular chassis.
 2. The modular front drivetrain ofclaim 1, wherein the modular front drivetrain comprises a singledrivetrain and suspension assembly that is configured to be installedonto and removed from the vehicle.
 3. The modular front drivetrain ofclaim 1, wherein the modular front drivetrain is configured tofacilitate a practitioner replacing an entire drivetrain and suspensionquickly and easily in the event of a part failure.
 4. The modular frontdrivetrain of claim 1, wherein the front suspension system includes anupper control arm and a lower control arm that are configured to couplethe front wheel with the modular chassis.
 5. The modular frontdrivetrain of claim 4, wherein the upper control arm comprises twoinboard upper control arm joints that couple the upper control arm tothe modular chassis and an outboard upper control arm joint that couplesthe upper control arm to the spindle assembly.
 6. The modular frontdrivetrain of claim 4, wherein the lower control arm includes twoinboard lower control arm joints that couple the lower control arm tothe modular chassis and an outboard lower control arm joint that couplesthe lower control arm to the spindle assembly.
 7. The modular frontdrivetrain of claim 4, wherein the upper control arm and the lowercontrol arm are configured to facilitate vertical motion of the frontwheel during travel over terrain and accommodate horizontal motion ofthe front wheel during steering of the front wheel by way of thesteering gear.
 8. The modular front drivetrain of claim 4, wherein astrut that is comprised of a shock absorber and a coil spring is mountedto the lower control arm by way of a lower pivot; and wherein a top ofthe strut is coupled to an upper pivot disposed on a chassis of thevehicle.
 9. The modular front drivetrain of claim 1, wherein thedrivetrain includes a transaxle, a front differential and a drive axlecoupled between each front wheel and the front differential.
 10. Themodular front drivetrain of claim 9, wherein the drive axle isconfigured to conduct torque from the transaxle to the front wheel andaccommodate vertical pivoting motion of the front suspension system inresponse to road conditions.
 11. The modular front drivetrain of claim9, wherein the drive axle includes a constant velocity joint that iscoupled with the spindle assembly and configured to allow uninterruptedtorque transmission from the transaxle to the front wheel duringvertical pivoting of the front suspension assembly due to roadconditions.
 12. The modular front drivetrain of claim 1, wherein thesteering system includes a steering rod coupled between each spindleassembly and a steering gear disposed on the modular chassis.
 13. Themodular front drivetrain of claim 12, wherein the steering gear isconfigured to cause the front wheels to articulate horizontally withrespect to the modular chassis upon the steering gear being turned byway of a steering wheel of the vehicle.
 14. The modular front drivetrainof claim 12, wherein the steering rod is coupled with each spindleassembly by way of a steering rod-end joint configured to allow verticaland horizontal rotational motion of the spindle assembly duringoperation of the vehicle.
 15. The modular front drivetrain of claim 14,wherein the steering rod-end joint is coupled with each spindle assemblyforward of a drive axle so as to provide a leading-edge steering systemto the vehicle.
 16. A method for a modular front drivetrain foroperating front wheels of a vehicle, the method comprising: configuringa modular chassis for supporting a drivetrain to convey torque from anengine onboard the vehicle to the front wheels; coupling each frontwheel to the modular chassis by way of a spindle assembly and a frontsuspension system; communicating torque from the drivetrain to the frontwheel by way of a front differential and drive axles; coupling a brakingsystem with the drive axles for slowing rotation of the front wheels;disposing a steering system on the modular chassis for directinghorizontal motion of the front wheels; and installing the modular frontdrivetrain onto the vehicle.
 17. The method of claim 16, furthercomprising configuring the modular front drivetrain as a singledrivetrain and suspension assembly to be installed onto and removed fromthe vehicle.
 18. The method of claim 16, wherein coupling includesconfiguring the front suspension system to allow vertical motion of thefront wheels due to road conditions.
 19. The method of claim 16, whereindisposing includes coupling a steering rod between each spindle assemblyand a steering gear disposed on the modular chassis.
 20. The method ofclaim 19, wherein coupling the steering rod includes coupling a steeringrod-end joint with each spindle assembly forward of the drive axles toprovide a leading-edge steering system to the vehicle.
 21. The method ofclaim 16, wherein communicating torque includes coupling each drive axlewith the spindle assembly by way of a constant velocity joint configuredto allow uninterrupted torque transmission from the transaxle to thefront wheel during vertical pivoting of the front suspension assemblydue to road conditions.